1. Technical Field
The present invention relates to a driver circuit for a stepping motor, which includes two coils and rotates a rotor driven by the coils by the setting of dissimilar phases of supply currents to these two coils.
2. Background Art
Among the various types of motors available, one representative type of motor capable of precisely determining position is a stepping motor. Stepping motors are widely utilized in various apparatuses, for example, in focusing and anti-shake mechanisms in cameras and in paper feed mechanisms in office automation equipment.
The stepping motor is generally driven by changing the rotating position of the rotor by a current phase to two stator coils. Therefore, if the rotor is rotated in accordance with the phase of current to the coils, the rotor rotates a predetermined amount regardless of the amount of current to the coils. Accordingly, the amount of current to the coils is generally set sufficiently large so that the rotor can rotate reliably.
There are demands to set the power consumption in electric equipment as low as possible. These demands are particularly high in office automation equipment requiring high current or battery driven portable equipment. On the other hand, in the drive of stepping motors, setting the amount of current to a magnitude at which the rotor rotates reliably means extra current flows to the coils and extra power is consumed. Furthermore, motor drive at high power causes irregular rotor rotation and also causes vibration, noise, and heat generation.